Sequence firing of jet motors



March 29, 1949ov R. QUEEN ETAL 29455992@ SEQUENCE FIRING OF JET MOTORS Filed Aug. 14, 1941i- Patented Mar. 29, 1949 SEQUENCE FIRING F JET MOTORS Roy L. Queen and Kenneth W. Hutchins, Pasadena, Calif., assgnors to Aerojet Engineering Corporation, Azusa, Calif., a corporation of Delaware Application August 14, 1944, Serial No. 549,412

4 Claims. 1

This invention relates to jet propulsion systems and particularly to successive systems in which charges of fuel placed in a combustion chamber are burned to create an exhaust jet.

The principal object of our invention is to prolong the exhaust jets which may be provided by such systems.

Jet propulsion motors have heretofore been used in which a charge of combustible material is cast or placed in a combustion chamber having an exhaust nozzle. To set the motor in operation the fuel is ignited by some suitable means, producing an exhaust jet of the gases of combustion; and this jet continues until the fuel in the chamber is burned. The duration of the jet from such motors has been limited to the length of time required to complete the combustion of the fuel charge placed in the motor; and this time has varied within a range, for example, of a few seconds to a minute or more.

Such jets of limited duration have been used to a considerable extent for assisting the takeoff of aircraft from runways. In many instances the desired time of the jet is greater than that of which the motor in inherently capable. In accordance with our invention we provide a system whereby the jet time may be prolonged. This is done by the provision of a `plurality of motors which are fired consecutively, the jet of the second motor commencing just about the time that the jet from the first motor is dying out and so on.

According to a feature of our invention we place a sequence switch at the portion of the propellant of a motor which is the last to burn so that the burning of this last portion of the propellant operates the sequence switch which operates the ignitor of the next successive jet motor.

The invention will be better understood from the following detailed description and the accompanying drawing in which:

Fig. 1v is an elevational View in cross section of our invention.

Fig. 2 is an elevational view in cross section of another embodiment of our invention; and

Fig. 3 is a schematic view of a wiring diagram involving our invention.

Similar numerals refer to throughout the several views.

similar parts In Fig. 1 we show a standard hydraulic switch I comprising a steel member 2 shaped in a manner to provide means for screwing the protruding nipple 3 into another member. Member 2 contains an orifice `4 which is counterbored in the shaped portion to receive a flexible washer 5 which may be of rubber. A copper disc 6 having its periphery turned up outwardly is placed against the exible washer 5. Two thin washers 'I and 8 respectively of insulating material sep arate the copper disc B from a steel disc 9. A small cylindrical actuator I0 made of fiber passes through the steel disc 9 and the two washers 'l and 8. A cup-shaped cylindrical member II is inserted into the counterbore. Member II is made of insulating material having in its bottom portion a spring bronze contactor I2 which is fastened by the lower connector I3. Contactor i2 has a loose arm I4 which contains a metal contact I5. Contact l5 is in line with the riveted head I'I of the upper connector It.

The standard hydraulic switch operates thus: When a pressure is exerted against the rubber washer 5 through orice 4, the copper disc E transmits this pressure through the cylindrical actuator ill upon the loose arm I4 which is thereby pushed outward and its metal contact I5 contacts the riveted head I'I. An electrical contact is thereby established. A pipe plug I8 has an orice I9 clear through which is threaded on both ends. Nipple 3 of the switch I is screwed into the outside end of orifice i9, while into the inside end thereof a tubular member 20 is screwed. The outside end of the orifice 4 is closed and the interior space 2l of the member 2U and orifices I9 and :i up to the rubber Washer 5 are filled with a volatile fluid or vaporizing solid.

Whether uid or solid is to be used depends entirely on the installation. In either case the medium used is such, which, when heated will expand and exert a pressure upon the hydraulic switch incorporated in this design. Such pressurev will close the switch, thereby permitting a current to flow through it, which actuates another ignitor for igniting the next jet motor.

In Fig. 2 we show another embodiment of our invention comprising a standard hydraulic switch I of the same construction as described under Fig. 1 which is screwed into a threaded plug I3. The pipe plug I8 has-a concentric orifice .|9. which is threaded in both ends. The thread in one end secures the standard hydraulic switch I and in the other Vend a tubular member 22 is screwed and welded. The outer end of the tubular member 22 is countersunk for receiving an infiammabl-e plug 23. The countersunk portion prevents the plug 23 from being forced into the tubular member 22. Plug 23 may be made of similar material as the solid propellant charge. i In Fig. 3 we show an electric wiring diagram for operating a plurality of jet thrust motors. Three of such motors are shown and are designated as 30, 3l, and 32 respectively. Each propulsion motor has a propellant charge 33, 34 and 35 respectively, and an ignitor 36, 3l, and 38 respectively. A sequence switch as shown in either Fig. 1 or Fig. 2 is embedded in the propellant and inserted into the bottom of the first two motors. These sequence switches are designated i0 and 4I respectively. A battery 42 is shown in the right hand lower corner of the drawing. Terminal 44 of the battery is in electrical contact with terminal I) of the ignitor 36 in motor and in further contact with the terminals 45 and 41 respectively of the sequence switches 40 and M respectively. The other battery terminal 43 is in electrical contact with one side of the main firing switch B0. The other side of the main firing switch is in contact with the terminals 5I, 53 and 55 respectively of the ignitors 36, 31, and 38, respectively in the motors 30, 3l, and 32 respectively. Terminal 46 of the sequence switch 40, in motor 39, is in contact with the terminal 52 of the ignitor 3l in motor 3|, terminal 43 of the sequence switch 4I in motor 3I is in contact with the terminal 54 of the ignitor 38 in motor 32.

The operation of the system as vshown in Fig. 3 is as follows: The closing of switch 6D permits electric current to flow from the battery 42 through the contacts and 5I of the ignitor 36 in motor 30. The energized ignitor 36 ignites the propellant 33 in motor 30, Motor 30 begins to fire, delivering the desired thrust while the propellant 33 is gradually used up. As the burning surface of the propellant reaches the level of the tip of the sequence switch 4U, which in this particular instance is the sequence switch shown in Fig. 1, the fluid contained therein expands under the heat, and closes the hydraulic brake switch I. The closing of this switch, 40 in Fig. 3, permits the current from the battery 44 to fiow through the ignitor 31 in motor 3l. The energized ignitor 3l ignites the propellant charge 34 in motor 3 I. Likewise the propellant charge 34 is used up. When the burning area of the propellant 34 reaches the tip of the sequence switch 4I in motorv3i, the heat of the charge actuates the sequence switch 4I, which closes the circuit be-A tween the battery 42 and the ignitor 38 of motor 32. A similar ignition ofthe propellant charge 35 in motor 32 takes place, which concludes the automatic sequential firing of the plurality of motors. It is understood that the plurality of such motors is not restricted to the number shown in Fig. 3.

When using the embodiment of the sequence switch shown in Fig. 2, the operation thereof is thus: When the burning surface area of the propellant reaches the combustible plug 23, it is immediately consumed opening the channel to the hydraulic switch. 'I'he pressure of the combustion chamber is immediately transmitted closing the hydraulic switch.4 Either' embodiment may be used, as each will produce the desired closing o! the hydraulic switch therein.

From the above detailed description it is evident that we have invented a useful automatic method of consecutively firing a plurality of Jet thrust motors after the first thrust motor has been started.

We claim:

1. A jet motor system comprising a plurality of jet motors each comprising a combustion chamber containing a propellant charge, igniting means for igniting the charge and a thermally operated electric switch located in the chamber of one motor at a position which is exposed t0 the heat of combustion when the charge has nearly completed its burning, said switch operating the ignitor of a second motor.

2. -In a system for'consecutive operation of a plurality of jet motors, each having a combustion chamber containing a propellant charge, the combination -comprising an electrically actuated ignitor attached to each of said motors for igniting the charge therein, a thermally operated switch in each but the last of said motors to operate in the sequential operation, each switch being positioned in its motor to be operated by the heat therein when the charge in the motor is near the end of its burning, a voltage source for actuating said ignitors, an electrical conductor connecting a first terminal of said voltage source with a first terminal of the ignitor in the first of the motors to operate and also to a first terminal of each of said switches, a second electrical conductor connecting the second terminal of the voltage source with the second terminal of each of saidrignitors, and an electrical conductor connecting the second terminal of each switch with the first terminal of the switch of the next of the motors to operate in the consecutive operation.

3. A system according to claim 2 in which each of the thermally operated switches is located in proximity to the part which is the last to burn of the propellant charge of its respective motor.

4. In a system of a plurality of jet motors, each motor having a combustion chamber and an exhaust nozzle, and ignitable propellant charges partly filling the chamber of each motor and presenting an exposed surface to a space Within the'chamber, said space being in communication with the nozzle, and an electrically operated ignitor in proximity to the exposed surface of the charge in each motor for firing the respective charge; the combination which comprises a switch attached to each motor excepting the last motor to operate in the successive operation, a switch of each motor being operable at or near the end of the burning of the charge of the motor, a voltage source for operating the ignitors, a first conductor connecting a first terminal of the voltage source with the second terminal of each of the ignitors of said motors, a second electrical conductor connecting the second terminal of the voltage source with the first terminal of the first motor to operate in the sequential operation, and to a first terminal of each of the switches, anda conductor connecting the second terminal of each switch with the first terminal of the ignitor of the next motor to operate in the sequential operation, and an operating switch in circuit with the voltage source for actuating the ignitor of the first motor to operate, thereby ignitingthe propellant in the last mentioned mo,l

tor, whereby when the propellant of said lastv mentioned vmotor burns down -to a point where l it operates the switch of the rst motor, the

closure of the last mentioned switch sends currentfrom the voltage source through the ignitor of the second motor to operate in the sequential operation thereby-starting it burning, and thus causing ignition of all the other motors in the system in their sequence.

' ROY L. QUEEN.

KENNETH W. HUTCHINS.

REFERENCES CITED The following references are of record in the nie of this patent:

Number Number 1 5,099

UNITED STATES PATENTS Name Date Wiren June 1, 1920 McBrien Oct. 11, 1927 Berkowitz Dec. 29, 1-931 Stolfa. et a1 Mar. 14, 1933 FOREIGN PATENTS Country Date Greet Britain Dec. 12, 1878 France Mar. 10, 1920 

